System and Method for Diagnosis and Treatment of a Breathing Pattern of a Patient

ABSTRACT

Described is a system including a sensor and a processing arrangement. The sensor measures data corresponding to a patient&#39;s breathing patterns. The processing arrangement analyzes the breathing patterns to determine whether the breathing patterns are indicative of a REM sleep state. In another embodiment, the processing arrangement analyzes the breathing patterns to determine whether the breathing patterns are indicative of one of the following states: (i) a wake state and (ii) a sleep state. In another embodiment, a neural network analyzes the data to determine whether the breathing patterns are indicative of one of the following states: (i) a REM sleep state, (ii) a wake state and (iii) a sleep state. In another embodiment, the processing arrangement analyzes the data to determine whether the breathing pattern is indicative of an arousal.

PRIORITY CLAIM

This application is a continuation-in-part of U.S. application Ser. No.11/210,568 filed Aug. 23, 2005, entitled “Positive Airway PressureSystem and Method for Treatment of Sleeping Disorder in Patient”, whichis a continuation of U.S. application Ser. No. 10/642,459 filed Aug. 14,2003 entitled “Positive Airway Pressure System and Method for Treatmentof Sleeping Disorder in Patient”, the entire disclosures of which areexpressly incorporated herein by reference.

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is a well recognized disorderwhich may affect as much as 1-5% of the adult population. OSAS is one ofthe most common causes of excessive daytime somnolence. OSAS is mostfrequent in obese males, and it is the single most frequent reason forreferral to sleep disorder clinics.

OSAS is associated with many conditions in which there is an anatomic orfunctional narrowing of the patient's upper airway, and is characterizedby an intermittent obstruction of the upper airway occurring duringsleep. The obstruction results in a spectrum of respiratory disturbancesranging from the total absence of airflow (apnea) to significantobstruction with or without reduced airflow (hypopnea and snoring),despite continued respiratory efforts. The morbidity of the syndromearises from hypoxemia, hypercapnia, bradycardia and sleep disruptionassociated with the apneas and subsequent arousals from sleep.

The pathophysiology of OSAS has not yet been fully worked out. However,it is well recognized that obstruction of the upper airway during sleepis in part due to the collapsible behavior of the supraglottic segmentof the airway resulting from negative intraluminal pressure generated byinspiratory effort. Thus, in patients suffering from OSAS, the upperairway during sleep behaves substantially as a Starling resistor (i.e.,the airflow is limited to a fixed value irrespective of the driving(inspiratory) pressure). Partial or complete airway collapse may thenoccur with the loss of airway tone which is characteristic of the onsetof sleep and which may be exaggerated in OSAS.

Since 1981, positive airway pressure (PAP) therapy applied by a tightfitting nasal mask worn during sleep has evolved as the most effectivetreatment for OSAS, and is now the standard of care. The availability ofthis non-invasive form of therapy has resulted in extensive publicityfor OSAS and the appearance of large numbers of patients who previouslymay have avoided the medical establishment because of the fear oftracheostomy. Increasing the comfort of the PAP system has been a majorgoal of research aimed at improving patient compliance with the PAPtherapy.

PAP therapy has become the mainstay of treatment in Obstructive SleepDisordered Breathing (OSDB), which includes Obstructive Sleep Apnea,Upper Airway Resistance Syndrome, Snoring, exaggerations of sleepinduced increases in the collapsibility of the upper airway and allconditions in which inappropriate collapsing of a segment of the upperairway causes significant un-physiologic obstruction to airflow. Thiscollapse generally occurs whenever pressure in the collapsible portionof the airway decreases below a level defined as a “critical tissuepressure” in the surrounding wall. The PAP therapy is directed tomaintaining pressure in the collapsible portion of the airway at orabove the critical tissue pressure at all times. In the past, this goalhas been achieved by raising a pressure delivered to the patient'sairway to a level higher than this critical tissue pressure at all timeswhen the patient is wearing the device.

In general, the need for the PAP therapy occurs only during sleep.However, the conventional PAP therapy has not taken sleep/wake stateinto account, and conventional PAP systems apply pressure unnecessarilywhen the patient is awake. The applied pressure is either a constantpressure, or a pressure based on breath-by-breath determination of theneed for treatment. Various strategies for determining the minimalpressure have evolved based on recognizing pathological events (e.g.,apnea, hypopnea and other evidence of high airway resistance)asdetermined by feedback from a variety of signals that indicate the needfor the PAP therapy due to the airway collapse.

Despite its success, limitations on the use of the conventional PAPsystems still exist based on, for example, discomfort from the mask andthe pressure required to obliterate the apneas. In particular, patientsoften report discomfort due to high pressure while being awake. To avoidthis discomfort, the applied pressure should be provided only when thepatient is asleep. For example, a “ramp” system utilizes a patientactivated delay in the onset of the applied pressure, but the rampsystem is not automatically responsive to patient awakenings during thenight, unless deliberately activated by the patient pushing a button.

Patient's discomfort during wakefulness is often associated with changesfrom a regular breathing pattern (e.g., near constant breath size andfrequency) to one which contains irregularities. These irregularpatterns (e.g., including isolated big breaths, short pauses, andchanges in breath flow shape that do not vary in any regular pattern)arerecognized by inspection of the airflow tracing alone, and frequentlyoccur when the patient is distressed by the PAP system.

Some conventional PAP systems utilize algorithms which continuously andautomatically titrate the applied pressure. These algorithms depend ondetecting evidence of airway collapse from the breathing signals.However, these algorithms of the conventional PAP systems have certainlimitations. For example, the irregular pattern of breathing presentwhile a subject is awake, and more so when anxious, interferes with theprocessing of the breath signal that calculates the applied pressure.

SUMMARY OF THE INVENTION

In one exemplary embodiment, the present invention relates to a systemincluding a sensor and a processing arrangement. The sensor measuresdata corresponding to a patient's breathing patterns. The processingarrangement analyzes the breathing patterns to determine whether thebreathing patterns are indicative of a REM sleep state.

In another embodiment, the present invention relates to a systemcomprising a sensor and a processing arrangement. The sensor measuringdata corresponding to the patient's breathing patterns. The processingarrangement analyzes the breathing patterns to determine whether thebreathing patterns are indicative of one of the following states: (i) awake state and (ii) a sleep state.

In a further embodiment, the present invention relates to a systemcomprising a sensor and a neural network. The sensor measuring datacorresponding to the patient's breathing patterns. The neural networkanalyzes the data to determine whether the breathing patterns areindicative of one of the following states: (i) a REM sleep state, (ii) awake state and (iii) a sleep state.

In yet another embodiment, the present invention relates to a systemcomprising a sensor and a processing arrangement. The sensor measuringdata corresponding to the patient's breathing patterns. The processingarrangement analyzes the data to determine whether the breathing patternis indicative of an arousal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary embodiment of a system according to thepresent invention;

FIG. 2 shows an exemplary embodiment of a method according to thepresent invention which utilizes the system shown in FIG. 1;

FIG. 3 shows a waveform of airflow during regular wakefulness of apatient (e.g., not anxious) who utilizes the system according to thepresent invention;

FIG. 4 shows a waveform of airflow during regular sleep in a patient;

FIG. 5 shows a waveform of airflow from a sleeping patient which isindicative of an elevated upper airway pressure resistance and hypopnea;

FIG. 6 shows a waveform of airflow from a sleeping patient which isindicative of a repetitive obstructive apnea;

FIG. 7 shows a waveform of airflow from a patient which is indicative ofa period of troubled wakefulness;

FIG. 8 shows a waveform of airflow from a patient which is indicative ofa period of REM sleep with irregular breathing due to phasic REM in apatient;

FIG. 9 shows a method for identifying a REM sleep state;

FIG. 10 shows a method identifying a sleep and a wake states of apatient;

FIG. 11 shows a method for training and utilizing a neural network foridentifying the patient's state; and

FIG. 12 shows a method for controlling a pressure supplied to a patient.

DETAILED DESCRIPTION

FIG. 1 shows an exemplary embodiment of a system 1 according to thepresent invention. The system 1 may include a mask 20 which is connectedvia a tube 21 to receive airflow having a particular pressure from aflow generator 22. The amount of pressure provided to a particularpatient varies depending on patient's particular condition. Such amountof pressure may be determined utilizing any conventional PAP therapymethods.

The mask 20 covers the patient's nose and/or mouth. Conventional flowsensors 23 are coupled to the tube 21. The sensors 23 detect the rate ofairflow to/from patent and/or a pressure supplied to the patent by thegenerator 22. The sensors 23 may be internal or external to thegenerator 22. Signals corresponding to the airflow and/or the pressureare provided to a processing arrangement 24 for processing. Theprocessing arrangement 24 outputs a signal to a conventional flowcontrol device 25 to control a pressure applied to the flow tube 21 bythe flow generator 22. Those skilled in the art will understand that,for certain types of flow generators which may by employed as the flowgenerator 22, the processing arrangement 24 may directly control theflow generator 22, instead of controlling airflow therefrom bymanipulating the separate flow control device 25.

The system 1 may also include a continuous leak port or other ventingarrangement 28. The venting arrangement 28 allows for gases contained inthe exhaled airflow of the patient to be diverted from the incomingairflow to prevent re-breathing of the exhaled gases.

FIG. 2 shows an exemplary embodiment of a method according to thepresent invention. In step 202, the patient initiates the system 1 byplacing the mask 20 over his face and powering up the generator 22, theflow control device 25 and the processing arrangement 24.

In step 204, the system 1 initiates a real-time monitoring procedure ofthe patient's breathing patterns. The monitoring procedure is performedby the processing arrangement 24 which may utilize pre-stored patientdata along with current data provided by the sensors 23 regarding theairflow to and from the patient and/or the applied pressure.

During the monitoring procedure, the processing arrangement 24 makes adetermination as to a current state of the patient (e.g., whether thepatient is asleep, awake and breathing regularly or awake and breathingirregularly due to distress or anxiousness). Such determination can bemade based on a number of different measurements. For example, theprocessing arrangement 24 may analyze the patient's heart rate, bloodpressure, EEG data, breathing patterns, etc. in the determining thepatient's state.

There are a number of characteristics of the patient's breathingpatterns that may be taken into account in making such a determination.FIGS. 3 and 4 show breathing patterns indicative of quiet, regular andrelaxed breathing in a patient during the PAP therapy. FIG. 3 isindicative of relaxed wakefulness (patient is not anxious ordistressed). FIG. 4 shows a period of relaxed breathing during sleepduring which the patient is correctly treated with the PAP therapy. Ineither case the applied pressure can be delivered without impairingcomfort. In addition, there are periods of sleep disordered breathingduring which the PAP therapy must be applied. Indices of sleepdisordered breathing include apnea (e.g., periods of zero airflow whichare greater than 8-10 seconds alternating with large breaths), hypopnea(e.g., cyclical periods of airflow which is substantially reduced,lasting 10 or more seconds, and terminated by larger breaths), orperiods of intermittent and cyclical change in the shape of the signal(e.g., characterized by flattening of the waveform, terminated by normalshaped breaths).

In contrast, the following exemplary characteristics may suggest thatthe patient is awake and anxious or distressed: pure mouth breathing(e.g., no signal from the sensors 23 which is configured to detect thepatient's airflow from the nose); erratic large breaths with varyinginspiratory times; irregularity of intervals between breaths (but notcyclic apneas which indicate sleep and the need for higher pressure,etc). FIG. 7 shows a period of such troubled wakefulness in which thebreathing pattern is characterized by irregularly variations in the sizeand/or frequency of breaths and/or irregular variation in the shapes ofthe patient's airflow tracing indicating that the patient is awake andeither anxious or uncomfortable. There is, however, no cyclical change(e.g., a periodic irregularity) in breath size, such as would be seenduring apnea and hypopnea sleep events. One of the ways to increase thepatient's comfort is to reduce the applied pressure when it is notneeded. Patients with obstructive sleep apnea do not require anypressure at all while awake. Thus, lowering the pressure applied to themask during such periods of irregular breathing should improve thepatient's comfort until the patient falls asleep (e.g., which .may bemarked by the resumption of regularity or cyclical but regular periodsof obstruction easily recognized as apnea and hypopnea or elevated upperairway resistance).

The above-described breathing patterns are distinguishable from the slowmodulation in breath size and inspiratory timing seen, e.g., in CheyneStoke and other forms of obstructive apnea. FIG. 5 shows a breathingpattern of a patient on the PAP therapy which includes an event ofelevated upper airway resistance and hypopnea during sleep and FIG. 6show a breathing pattern corresponding to a repetitive obstructiveapnea. In both cases, the changes in breath size and frequency areslowly modulated and repetitive and cyclical (e.g., regularlyirregular). In these periods, the applied pressure is either needed ormust be raised, but there is no indication it is contributing to patientdistress. Thus, the applied pressure should not be lowered.

FIG. 8 shows a period of REM sleep. In this phase of sleep, whichoccurs, e.g., for 10-30 minutes every 90 minutes of normal sleep, abreathing pattern is often characterized by irregular breathing. Thispattern represents a potential exception to the use of irregularity toindicate wakefulness with anxiety. However, during this type ofbreathing, the patient is asleep and the applied pressure must bemaintained (i.e., not reduced as during wakefulness). The type ofirregularity seen during REM differs from that seen in wakefulness inseveral key parameters. This REM associated pattern of breathing mayinclude, e.g., the absence of larger breaths, especially after pauses,generally high respiratory rates and low flow rates, and a tendency forclustering of small breaths. These differences in the pattern of therespiratory airflow signal from those seen during troubled wakefulnessallow the separation of these states and can be used to make a change inthe applied pressure.

The processing arrangement 24 also collects and records data for eachpatient. Such data may be collected and entered manually by a technicianor automatically by the processing arrangement 24 itself. For example,the technician may monitor the patient's breathing and simultaneouslydetermine whether the patient is awake. Then, when the patient fallsasleep, the technician may mark the breathing patterns of this sleepingpatient so that the processing arrangement 24 may utilize this data infuture determinations as to whether or not the patient is awake. When adatabase of the patient's breathing characteristics has been built,determinations as to the patient's wakefulness may be made significantlymore accurate.

In step 206, the processing arrangement 24 determines whether there hasbeen a change in the patient's state. For example, the processingarrangement 24 may determine whether the patient was asleep and has beenawakened; or the patient was awake and has fallen asleep. If there hasbeen no change, the processing arrangement 24 continues with themonitoring procedure.

If there has been a change in the patient's state, the processingarrangement 24 adjusts the pressure to correspond to the patient'scurrent state (step 208). For example, if the patient has been awakenedand the patient's breathing patterns indicate a period of troubledwakefulness as shown in FIG. 7, the processing arrangement 24 may reducethe applied pressure provided to the patient during such period. Thisreduction may be a complete elimination of the applied pressure (i.e.,the flow generator 22 reduces the flow rate to a level which does notprovide any net pressure to the patient in the mask, while maintainingonly the minimum sufficient flow through the circuit to the ventingarrangement 28 to prevent CO2 buildup), or a partial reduction (i.e.,the flow generator 22 produces only the flow sufficient to maintain areduced portion of the air pressure that it generates while the patientis asleep).

On the other hand, if the patient has fallen asleep, the processingarrangement 24 may instruct the flow control device 25 to elevate thepressure to the level to be applied while the patient is asleep. Forexample, this may be indicated where the patient's breathing patternschanged from the pattern shown in FIG. 7 to the pattern shown in FIG. 4.In such a case, the processing arrangement 24 should increase thepressure. From that time on, this increased pressure should not bereduced unless one of a plurality of predetermined breathing patterns isdetected. For example, the processing arrangement 24 should at leastmaintain the same pressure or, preferably, increase the pressure if thepatient's breathing pattern indicates an event of elevated upper airwayresistance and hypopnea as shown in FIG. 5. Also, the pressure should beat least maintained at the same value, or, preferably, increased, if thepatient's breathing pattern indicates a repetitive obstructive apnea asshown in FIG. 6, or if the patient shows irregular breathing whichsuggests he is in REM sleep, as during this type of breathing thepatient is asleep and the applied pressure must be maintained at thesame level as during other periods of sleep (i.e., not reduced as duringwakefulness).

In step 210, the processing arrangement 24 determines whetherinstructions to disengage the system 1 have been given. If suchinstructions have been given (e.g., if the patient has pressed adesignated button or a preset time limitation has expired), the system 1shuts down and ends all monitoring and flow generating activities.Otherwise, the system 1 continues with the monitoring procedure of step204.

One of the advantages of the system 1 according to the present inventionis that the pressure supplied to the patient is adjusted (e.g., reducedto zero or a preset low level) when the patient has an irregularbreathing pattern that suggests that he is awake and anxious. Whenbreathing is either regular (e.g., suggesting sleep) or shows sleepdisorder breathing events, the pressure may be maintained or increased.

In another embodiment of the present invention, the system 1 may beutilized for one or more diagnostic applications. That is, theprocessing arrangement 24 may obtain data from the sensors 23 regardingthe breathing patterns of the patient and record the patient's statewithout supplying the pressure thereto. For example, the presentinvention may include a method 100 as shown in FIG. 9 for determiningwhen the patient is in the REM sleep state. In step 102, the system 1 isinitialized and the mask 20 is coupled to the patient. In step 104, thesensors 23 obtain data indicative of the patient's breathing patterns.

In step 106, the processing arrangement 24 determines whether thebreathing pattern is identifiable as the REM sleep state. For example,when the breathing pattern includes the absence of large breaths (e.g.,after pauses in breathing), a high respiratory rate and a low flow rateand/or a tendency for clustering of small breaths, the processingarrangement 24 may identify the breathing pattern as the REM sleepstate. When the breathing pattern is not identified as the REM sleepstate, the processing arrangement 24 may continue to gather dataregarding the patient's breathing patterns.

In step 108, the processing arrangement 24 has identified the breathingpattern as the REM sleep state and reports such to a user (e.g., aphysician) of the system 1. Additionally or alternatively, theprocessing arrangement 24 may flag a portion of an internal log to notethat the patient was in the REM sleep state for a predefined time. Thatis, after the REM sleep state has been identified, the processingarrangement 24 may continue identifying the breathing patterns of thepatient to determine a termination of the REM sleep state.

In a further embodiment of the present invention, the system 1 may beutilized to detect when the patient is asleep/awake and adjust pressurebased thereon. A method 250 according to this embodiment is shown inFIG. 10. In step 252, the system 1 is initialized and coupled to thepatient. In step 254, the processing arrangement 24 determines a firststate of the patient based on data obtained from the sensors 23regarding the breathing pattern of the patient. In this embodiment, theprocessing arrangement 24 may determine whether the patient is in asleep state or a wake state based on the breathing pattern. That is, thedata may be indicative of a regular breathing state which is generallyidentified with the sleep state or the wake state.

In another embodiment, the processing arrangement 24 may detect whether,for example, the patient is in the sleep state. That is, the system 1may be applied when the patient is in the wake state. After the system 1is initialized, the processing arrangement 24 may default to assumingthat the patient is in the wake state. Thus, the processing arrangement24 may only detect whether the patient is in the sleep state, and whenthe sleep state is not detected, default to assuming that the patient isin the wake state.

In step 256, the processing arrangement applies supplies the airpressure as a function of the state. In one embodiment, the CPAP may beapplied at a first level for the sleep state and a second level for thewake state. In another embodiment, an automatically adjusting CPAP(“auto-CPAP”) may be applied. In this embodiment, the processingarrangement 24 may adjust the pressure toward the first level when thesleep state is identified, and toward the second level when the wakestate is identified. Those of skill in the art will understand that,using this embodiment, a total sleep time of the patient may bedetermined by the processing arrangement 24 based on identification ofthe sleep and wake states.

In another embodiment of the present invention, the system 1 may includea neural network coupled to the processing arrangement 24 and thesensors 23 for identifying the state of the patient. The neural networkmay obtain data from the sensors 23 and determine the state of thepatient based on the data. Before and/or during operation of the neuralnetwork, it may be trained to identify characteristics of the breathingpatterns which correspond to one or more of the states.

FIG. 11 shows an exemplary embodiment of a method 300 for implementingthe neural network according to the present invention. In step 302, theneural network is constructed for identifying the patient's state ofrespiration. In one embodiment, the neural network comprises a pluralityof nodes including input, hidden and output nodes. A predeterminednumber of the output nodes may equal a number of the states beingidentified. For example, the neural network may include four outputnodes when identifying the following states: (i) a regular breathingstate, (ii) a sleep disorder breathing state, (iii) a REM sleep stateand (iv) a troubled wakefulness state.

In step 304, the neural network is trained using sample breath dataobtained by the input node. The sample breath data may be known by theoperator of the system 1 to correspond to one of the states. Forexample, the sample breath data may be manually scored for thecorresponding state. In step 306, the neural network is tested usingtest breath data. The test breath data may differ from the sample breathdata, but may be known by the operator of the system 1 to correspond toone of the states. In step 308, it is determined whether the neuralnetwork is performing satisfactorily. If not, the training is resumed.

In step 310, the neural network has been trained and is performingsatisfactorily, so it is utilized to detect the patient's state. Theprocessing arrangement 24 obtains breath data from the sensors 23 andmeasures a predetermined number of parameters of the breath data. Thebreath data may be obtained for a predetermined number of breaths (e.g.,5 breaths). The parameters may include, but are not limited to a peakflow, an inspiration time, an expiration time, a frequency and a totalbreath time. Although, the present invention will be described withrespect to measurement of the parameters for individual breaths, thoseof skill in the art will understand that the parameters may be measuredfor any number of consecutive breaths or breaths having a predeterminedtime/breath interval therebetween.

A summary of the measurements may be generated which may include amedian, a mean, a range and a standard deviation for each parameter.Further, a difference in each parameter between consecutive breaths maybe identified. The difference(s) may be included in the summary. Withinthe summary, the breaths may be sorted in a predefined order (e.g.,ascending, descending) based on one or more of the parameters.

The summary may then be input into the input node of the neural network.The neural network may then identify the summary and/or each breath withthe output node corresponding to the state of the patient. For example,in one instance, the summary may indicate that the patient is in theregular breathing state. In another instance, one breath may beindicative of the regular breathing state, while another breath withinthe predetermined number of breaths is indicative of the troubledwakefulness state.

After or while identifying the state, the processing arrangement 24 maybe obtaining further breath data for a further predetermined number ofbreaths following a last breath of the predetermined number of breaths.Once the state has been identified, the processing arrangement 24 mayadjust the pressure supplied to the patient based on the state.

In a further exemplary embodiment of the present invention, theprocessing arrangement 24 may utilize a predetermined algorithm foradjusting the pressure after the state of the patient has beenidentified. A method 400 according to this embodiment is shown in FIG.12. In step 402, the system 1 is initialized and the processingarrangement 24 supplies the pressure to the patient at a default level.

In step 404, the processing arrangement 24 determines whether thepatient's breathing pattern is indicative of the sleep disorderbreathing state. In step 406, when the sleep disorder breathing statehas been detected, the processing arrangement 24 increases the pressurein predetermined increments toward a first predetermined pressure (e.g.,a therapeutic pressure). According to this embodiment, any furtherdetection of the sleep disorder breathing state may increase a rate atwhich the pressure is increased (e.g., decrease time betweenincrements).

In step 408, the processing arrangement 24 determines whether thepatient's breathing pattern is indicative of the troubled wakefulnessstate. In step 410, when the troubled wakefulness state has beendetected, the processing arrangement 24 decreases the pressure in thepredetermined increments toward a second predetermined pressure (e.g., apressure more comfortable during the wake state). According to thisembodiment, any further detection of the troubled wakefulness state mayincrease a rate at which the pressure is increased.

During the execution of the method 400, when the processing arrangement24 determines that the patient's breathing pattern is indicative of theregular breathing state and/or the REM sleep state, the pressure may besupplied as previously specified. For example, while the pressure isbeing increased because the sleep disorder breathing state was detected,and the processing arrangement 24 detects the regular breathing state,the pressure may continue to be increased toward the first predeterminedpressure. That is, anywhere within the method 400, the processingarrangement 24 may detect or be detecting whether the patient'sbreathing pattern is indicative of the regular breathing state and/orthe REM sleep state.

Also according to the above embodiment, the processing arrangement 24may be utilized in an auto-CPAP mode. In this manner, the processingarrangement 24 automatically maintains and/or adjusts the pressure.However, when the troubled wakefulness state is detected, the processingarrangement 24 may decrease the pressure in the predetermined incrementstoward the second predetermined pressure. When any other state isdetected, the processing arrangement 24 automatically reverts to theauto-CPAP mode.

In yet a further embodiment of the present invention, the system 1 maybe utilized to detect a predetermined flow event such as, for example, adisruptive breathing pattern indicative of transient or sustainedarousal as, for example, a large breath during a period of regularbreathing suggesting a transient 3-5 seconds arousal or sustainedarousal as measured by EEG.)

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the structure and themethodology of the present invention without departing from the spiritor scope of the invention. Thus, it is intended that the presentinvention cover all modifications and variations of this invention whichcome within the scope of the appended claims and their equivalents.

1-22. (canceled)
 23. A positive airway pressure system for delivery of a flow of breathable gas at a positive treatment pressure with respect to ambient air pressure delivered to an entrance of a patient's airways in order to assist in treating a sleeping disorder in a patient, the positive airway pressure system comprising: a flow generator which supplies a positive treatment pressure flow of breathable gases to be supplied to a patient; a flow sensor located in a flow path of the positive treatment pressure flow of breathable gases, the flow sensor measuring data corresponding to the flow of breathable gases directed to the patient and indicative of the patient's breathing patterns; and a processing arrangement which receives the measured data corresponding to the flow of breathable gases from the flow sensor and analyzes the data to determine the patient's breathing patterns, the processing arrangement also determines whether to alter the pressure supplied by the flow generator to the airway of the patient based, at least in part, on the determined breathing patterns of the patient, wherein the processing arrangement automatically delays the onset of a pressure increase to the patient when the processing arrangement determines that the patient is in an awake state, wherein the delay lasts at least until the processing arrangement determines that the patient is in an asleep state.
 24. The system of claim 23, wherein when the processing arrangement determines during an asleep state that the patient is experiencing an elevated upper airway resistance, the processing arrangement increases the pressure applied to the airway of the patient.
 25. The system of claim 23, wherein when the processing arrangement determines during an asleep state that the patient is experiencing a hypopnea event, the processing arrangement increases the pressure applied to the airway of the patient.
 26. The system of claim 23, wherein when the processing arrangement determines during an asleep state that the patient is experiencing an apnea event, the processing arrangement increases the pressure applied to the airway of the patient.
 27. The system of claim 23, wherein when the processing arrangement determines that the patient has transitioned to an awake state from an asleep state, the processing arrangement lowers the pressure applied to the airway of the patient.
 28. The system of claim 27, wherein the awake state is a troubled wakefulness state.
 29. The system of claim 23, wherein the pressure is increased using a ramp system.
 30. The system of claim 23, wherein the processing arrangement determines that the patient is in an asleep state when the breathing pattern is a period of regular breathing.
 31. The system of claim 23, wherein the processing arrangement determines that the patient is in an asleep state when the breathing pattern indicates a pattern of hypopnea events.
 32. The system of claim 23, wherein the processing arrangement determines that the patient is in an asleep state when the breathing pattern indicates a pattern of obstructive apnea events.
 33. The system of claim 32, wherein the pattern of apnea events is at least three obstructive apnea events.
 34. The system of claim 23, wherein when the processing arrangement determines that the patient has transitioned between at least an awake state and an asleep state and is experiencing a hypopnea event, the processing arrangement automatically increases the pressure to a treatment pressure.
 35. The system of claim 23, wherein when the processing arrangement determines that the patient has transitioned between at least an awake state and an asleep state and is experiencing an apnea event, the processing arrangement automatically increases the pressure to a treatment pressure.
 36. The system of claim 23, wherein when the processing arrangement determines that the patient has transitioned between at least an awake state and an asleep state and is experiencing elevated upper airway resistance, the processing arrangement automatically increases the pressure to at least a first treatment pressure. 